One goal in designing vehicles, especially aero-structures of airplanes and other aircraft, is to reduce unwanted drag. An aircraft, or portions thereof, may be configured to have an aerodynamic shape, but drag also may be addressed by reducing exterior surface discontinuities such as seams between joined sections, joints (such as hinges, etc.) between fixed and moving control surfaces, and so forth. Such discontinuities not only represent potential sources of vortex-induced drag, but also may create or increase the acoustic signature of the aircraft, and/or other signatures including optical, radio frequency (RF), electrical, and so forth.
Some proposed measures focus on closing gaps between fixed and moving control surfaces with moveable structure such as sliding plates, but this adds mechanical complexity. Alternatively, such discontinuities may be sealed, such as by covering and/or forming the aircraft skin with a flexible material, but many flexible materials lack the appropriate shear strength to withstand the forces that are typically applied to an aircraft skin. Composite materials may have suitable mechanical properties, as well as generally high strength-to-weight ratios as compared to other structural materials, such as metal. However, once formed, many composites are too rigid and/or brittle to cover or close a gap between a fixed and a moving surface.
There is therefore a need for materials suitably flexible to cover or form an aircraft skin and having the mechanical stability appropriate to the forces typically applied thereto.